Vacuum processing facilities are systems in which workpieces or substrates are processed respectively treated in a processing room under vacuum conditions, in other words at ambient pressures below the atmospheric pressure. Such systems are known in the state of the art and are used for thermal treatments, coatings, etching processes and many other processes under reduced pressure conditions.
Many types of vacuum processing facilities use gates (load locks) in order to use a volume—smaller in comparison with the processing room—for inserting and removing the workpieces in the processing room. The advantage is that this smaller volume can be pumped out (evacuated) faster than the processing room, which thus can be maintained for longer below a low target pressure. Furthermore, in this manner, the processing room can more easily be kept free from harmful ambient gases such as water vapor, volatile organic compounds etc. Some of these contaminations can be removed only with difficulty by means of vacuum pumps, which is why the pumping output is often assisted by so-called Meissner traps. Broadly speaking, a Meissner trap constitutes a cooled condensation surface for trace gases respectively residual gases, primarily for water vapor under vacuum. They are generally made as conduits of copper or stainless steel that are placed in the vacuum chamber in the form of spirals or flat in a meandering pattern in order to provide a cooled surface that is as large as possible. Most commonly, commercially available non-CFC coolants or liquid gases (e.g. N2) can be contemplated as cooling liquids.
The cooling liquid must be directed from a source (e.g. cooling unit, storage tank) into and again out of the vacuum processing chamber by means of insulated lines. For this, vacuum-insulated lines are commonly used in which a flexible line or conduit in an external, vacuum-sealed protective sleeve is guided. The intermediate space between the coolant line itself and the external sleeve is evacuated so that the heat loss to the environment is minimized. Such vacuum lines are commercially available, they can be bought ready to use (pre-evacuated). The intermediate space is often provided with getter material that can compensate for possible leakages or residual gases. The lines are connected via vacuum feed-through in the processing chamber wall with the Meissner trap which, depending on the type of use, can be in the processing room or in a gate/lock.